A new endothelin converting enzyme (ECE) inhibitor, TMC-66 was isolated fro
m the fermentation broth of Streptomyces sp. A5008. The structure of TMC-66
was elucidated by spectroscopic analyses to be a new member of benzo[a]nap
hthacenequinone class of antibiotics. TMC-66 had a highly selective inhibit
ory activity for ECE with an IC50 value of 2.9 mu M. Taxonomy of the produc
ing strain is also described.